Data retrieving method, data retrieving apparatus, data compression apparatus method and data compression apparatus

ABSTRACT

A data compression apparatus has a characterizing point extracting part 1 which extracts data expressing characterizing points included in a plurality of data showing a result of carrying out simulation, quantized data generating part 2 which generates quantized data obtained by quantizing data except for data expressing characterizing points, and file number converting part 3 which converts the same types of quantized data including in the quantized data, into a relating file number. In the case of compressing data, data except for the characterizing points is compressed. If the same quantized data is included at the same address location in the previously-compressed file, the quantized data is replaced with the file number of previously-compression file, thereby compressing data at high efficiency.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Applications No. 2001-227848, filed onJul. 27, 2001, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a data compression method and adata retrieving method. For example, the present invention aims at atechnique for compressing/retrieving data expressing a result ofcarrying out simulation.

[0004] 2. Related Background Art

[0005] When designing semiconductor devices and so on, numericalanalysis such as computer simulation became absolutely imperative. Asstructures to be designed become complex, the amount of data showing acomputed result increases. The simulation is often carried out whilechanging simulation conditions such as an applied voltage and time.Because of this, it is necessary to preserve the simulation result foreach of the different simulation conditions.

[0006] Conventionally, the simulation results were preserved as it is orafter compressing the simulation results. As a method of performing thecompression, a method of preserving the number of times of repetition ofdata “1” and “0” described by binary code is known.

[0007] When the amount of data increases, computer resources such as ahard disk drive is significantly consumed, and data management becomescomplex and troublesome.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a datacompression method capable of compressing data at high compression ratioby a simplified method.

[0009] Furthermore, the other object of the present invention is toprovide a data retrieving method capable of retrieving the compresseddata at high compression ratio by a simplified method.

[0010] According to embodiments of the present invention, a dataretrieving method of retrieving compression data including non-quantizeddata expressing characterizing points and quantized data except for saidcharacterizing points, comprising:

[0011] carrying out simulation by setting said non-quantized data asfixed values, if necessary based on said quantized data; and

[0012] retrieving data before quantization from said quantized databased on a result of carrying out said simulation.

[0013] Furthermore, according to embodiments of the present invention, adata retrieving method of retrieving compression data includingnon-quantized data expressing characterizing points, quantized dataexcept for said characterizing points, and pointer data related tocertain quantized data comprising:

[0014] converting said pointer data into the corresponding quantizeddata;

[0015] carrying out simulation by setting said non-quantized data asfixed values and an initial value based on said quantized data; and

[0016] retrieving data before quantization from said quantized databased on a result of carrying out said simulation.

[0017] Furthermore, according to embodiments of the present invention, adata compression method, comprising:

[0018] extracting data expressing characterizing points from a pluralityof data as objection of compression;

[0019] generating quantized data to quantize data except for dataexpressing said characterizing points among said plurality of data asobjection of compression;

[0020] converting the same types of quantized data included in saidquantized data into pointer data having the number of bits fewer thanthat of said quantized data, said pointer data being related to thecorresponding quantized data.

[0021] Furthermore, according to embodiments of the present invention, adata retrieving apparatus which retrieves compression data includingnon-quantized data expressing characterizing points and quantized dataexcept for said characterizing points, comprising:

[0022] a simulation part for carrying out simulation by setting saidnon-quantized data as fixed values and if necessary setting initialvalues based on said quantized data; and

[0023] a first data retrieving part for retrieving data beforequantization from said quantized data, based on a result of saidsimulation.

[0024] Furthermore, according to embodiments of the present invention, adata retrieving apparatus which retrieves compressing data includingnon-quantized data expressing characterizing points, quantized dataexcept for said characterizing points, and pointer data related tocertain quantized data, comprising:

[0025] a quantized data converting part which converts said pointer datainto the corresponding quantized data;

[0026] a simulation part for carrying out simulation by setting saidnon-quantized data to be fixed values and initial values based on saidquantized data; and

[0027] a first data retrieving part for retrieving data beforequantization from said quantized data based on the result of thesimulation.

[0028] Furthermore, according to embodiments of the present invention, adata compression apparatus, comprising:

[0029] a data extraction part for extracting data expressingcharacterizing points from a plurality of data as objection ofcompression;

[0030] a quantized data generating part which generates quantized dataobtained by quantizing data except for data expressing saidcharacterizing points among said plurality of data as objection ofcompression; and

[0031] a pointer converting part for converting the same types ofquantized data included in said quantized data into pointer data havingthe number of bits fewer than that of the quantized data, said pointerdata being related to the quantized data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a block diagram of a first embodiment of a datacompression apparatus according to the present invention;

[0033] FIGS. 2A-2B are diagrams showing a plurality of files showing aresult of carrying out simulation;

[0034]FIG. 3 is a diagram showing state in which simulation object isdivided into mesh shape;

[0035]FIG. 4 is a flowchart showing processing procedure of a datacompression apparatus of FIG. 1;

[0036]FIG. 5 is a diagram showing an example of the loaded file;

[0037]FIG. 6 is a diagram showing data distribution before quantization;

[0038]FIG. 7 is a diagram showing data distribution after quantization;

[0039]FIG. 8 is a diagram of describing processing procedure of step S6described in FIG. 4;

[0040]FIG. 9 is a diagram in which processing procedure of datacompression is modified;

[0041]FIG. 10 is a flowchart showing a characterizing point extractingprocessing in step S3 described in FIG. 4;

[0042]FIG. 11 is a diagram showing a control volume;

[0043]FIG. 12 is a block diagram showing schematic configuration of oneembodiment of a data retrieving apparatus according to the presentinvention;

[0044]FIG. 13 is a flowchart showing processing procedure of a dataretrieving apparatus described in FIG. 12;

[0045]FIG. 14 is a diagram in which processing procedure of retrievingdata is modified;

[0046]FIG. 15 is a diagram showing a general equation of matrixsolution;

[0047]FIG. 16 is a cross sectional diagram of a transistor fordescribing one example of semiconductor analysis;

[0048]FIG. 17 is a diagram showing physical quantity of the surroundinglattice points of the characterizing points having the physical quantityX4;

[0049]FIG. 18 is a diagram showing physical quantity of the surroundinglattice points of the characterizing points having the physical quantityψ;

[0050]FIG. 19 is a flowchart showing data compression processingprocedure in a second embodiment of the present invention;

[0051]FIG. 20 is a conceptual diagram of data compression processingprocedure described in FIG. 19;

[0052]FIG. 21 is a flowchart showing data compression processingprocedure in a third embodiment of the present invention; and

[0053]FIG. 22 is a conceptual diagram of data retrieving processingprocedure described in FIG. 21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] Hereinafter, a data retrieving apparatus and a data compressionapparatus according to the present invention will be more specificallydescribed with reference to drawings. Furthermore, the present inventionis never limited to the following embodiments, and can be modified invarious forms.

[0055] (First Embodiment)

[0056]FIG. 1 is a block diagram of a first embodiment of a datacompression apparatus according to the present invention, whichcompresses a result of carrying out simulation.

[0057] This data compression apparatus has a characterizing pointextracting part 1 for extracting data expressing characterizing pointsfrom a plurality of data expressing the result of carrying out thesimulation, a quantized data generating part 2 for generating thequantized data obtained by quantizing data except for data expressingthe characterizing points, and a file number converting part 3 forconverting the same type of quantized data included in the quantizeddata into a relating file number.

[0058] The result of carrying out the simulation inputted to the datacompression apparatus of FIG. 1 includes N pieces of files sorted foreach condition of the simulation. FIG. 2A shows an example of N=5. Asshown in FIG. 2B, these N pieces of files may be divided by prescribeddelimiter information and integrated into one consolidated file.

[0059] A simulation object is divided into mesh shape as shown in FIG.3, and the data expressing the result of carrying out the simulation foreach mesh is included in each file.

[0060] The simulation is carried out for each lattice point of the meshor for each reference range enclosed by the mesh. The locations forcarrying out the simulation is managed by addresses. For example, ifassumed that each of lattice points of FIG. 3 is the location forcarrying out the simulation, the result of carrying out the simulationfor each address (they are also called index) expressing the locationsof the lattice points is stored in the file.

[0061]FIG. 4 is a flowchart showing processing operation of the datacompression apparatus described in FIG. 1. First of all, if thecompression requirement by users with regard to the result of carryingout the simulation is received, a variable n for counting the number oftimes of repetition of the processings is initially set to be “1” (stepS1).

[0062] Next, nth file is loaded (step S2). “Load” means for performingsome kind of processings for the file in order to carry out datacompression. More specifically, the file is copied to a work memory ofthe computer, or is copied to a work region of a recording medium suchas a hard disk drive. Or instead of copying the file by itself to thework memory and the recording medium, the system may only acquire thestoring address of the file on the recording medium. Or after readingthe file in the block into a temporary memory region, the flowchart ofFIG. 4 may be carried out.

[0063]FIG. 5 is a diagram showing an example of the loaded file. Aplurality of data corresponding to addresses showing the locations ofcarrying out the simulation is included in the file. That is, each datais managed by the addresses. Hereinafter, it will be simply assumed thatall the data has the same data structure.

[0064] Next, the characterizing point extracting part 1 extracts data tobe the characterizing points included in the file (step S3). The methodof extracting the characterizing points will be described later.

[0065] Next, data except for the charactering points is quantized (stepS4). The quantization is performed by using a conventional method. Morespecifically, the range of values of data candidate are divided into,for example, 256 levels, the level of the actual data is checked, andthe quantization level is expressed by the binary code of 8 bits.

[0066] In numeric calculation such as the simulation, because the actualdata is a real number value of 16-64 bits, by compressing it into dataof about 8 bits at the stage of the quantization, it is possible toconsiderably reduce the amount of data.

[0067]FIG. 6 is a diagram showing data distribution before thequantization, X and Y axes of 3D coordinates show X and Y coordinates,respectively, and Z axis shows physical quantity of data. When thequantization processing is performed for FIG. 6, a distribution such asFIG. 7 is obtained. Compared with the original distribution, theamplitude of the physical quantity is limited, and rough distribution isobtained. By such a quantization, it is possible to reduce the number ofbits of data, and to compress data by itself. The method of retrievingthe original distribution of FIG. 7 from the rough distribution of FIG.6 will be described later.

[0068] After the quantization in step S4 of FIG. 4 is finished, it isdetermined whether or not there are the previously-compressed files(step S5). The determination processing is carried out only in the caseof n>1, and the processing is omitted in the case of n=1. When there isthe previously-compressed file, data in the file is compared with thatin the file in now progress (step S6). More specifically, the data ofthe same address in both files are compared with each other. If thequatization level of both data compared with each other is the same, thecorresponding data in the file in now progress is replaced with apointer data (for example, file number) for designating thepreviously-compressed file.

[0069]FIG. 8 is a diagram for describing the processing contents of stepS6. There are six pieces of data with file numbers 1-6 in thepreviously-compressed files. The quantized data “01001010” is stored inthe file number 1, and the same data as that of the file number 1 isstored as the file number 2. In this case, practically, four bit data“0001” to intend for the file number 1 is stored as the file number 2.Similarly, the quantized data “10111011” is stored as the file number 3.The four bit data “0011” to intend for the same data as that of the filenumber 3 is stored as the file numbers 4 and 5. The quatization data“11011001” is stored as the file number 6.

[0070] If the data in now progress is the quatization data “10111011”,which is the same data as that of the file number 3, its data isconverted into four bits data “0011” to intend for the file number 3.

[0071] When determined that there is no previously-compressed file instep S5 of FIG. 4, or when the processing of step S6 is finished, it isdetermined whether or not a variable n is equal to a repeated maximumnumber N of the processings (step S7). If n<N, the variable n is countedup by “1” (step S8), and then the processings after step S1 arerepeated. If n=N, data obtained by compressing the result of carryingout the simulation and simulation operation information necessary whenretrieving data are outputted (step S9). Here, the simulation operationinformation is, for example, input files of the simulation, a name of asimulator used for carrying out the simulation and a version number ofthe simulator.

[0072]FIG. 9 is a diagram of modifying the processing procedure of datacompression. First of all, the file before compression including aplurality of data is loaded (state 0), and then the characterizingpoints are extracted (state 1). In FIG. 9, data of the characterizingpoints is displayed by black color, and the other data is displayed bywhite color.

[0073] Next, data except for the characterizing points is converted intothe quantized data (state 2). Next, if the previously-compression datais existed in data in now progress, the data is converted into the filenumber of the previously-compression data.

[0074]FIG. 10 is a flowchart showing the characterizing point extractionprocessing of step S3 described in FIG. 4. This flowchart aims at dataexpressing space distribution of the physical quantity, detects pointsin which space variation of the space distribution is sharpest, and setsdata within 90% of these points as the characterizing points.

[0075] First of all, a variable k is initialized to “1”, and adivergence maximum value DXmax is initialized to “0” (step S21). Next,the divergence ∇X(k) of kth data is calculated (step S22). Thecalculation of divergence is, for example, as shown in FIG. 11,performed based on a control volume method of equation (1).

∇X(k)äx*(Xkn−Xk)/Ärn+äx*(Xks−Xk)/Ärs+äy*(Xke−Xk)/Äre+äy*(Xkw−Xk)/Ärw  (1)

[0076] Here, δx and δy are expressed by equations (2) and (3),respectively.

äx=0.5*(Ärw+Äre)  (2)

äy=0.5*(Ärn+Ärs)  (3)

[0077] The calculation result of the divergence ∇X(k)is stored into thetemporary preservation file (step S23). Next, if the calculation resultis larger than DXmax, the calculation result of ∇X(k)is substituted intoDXmax (step S24). The “max( )” in the flowchart of FIG. 10 is a functionfor returning a maximum value in arguments.

[0078] Next, it is determined whether or not to be k<K (step S25). IfYES, the variable k is incremented by “1”, and then the processingsafter step S22 is repeated. If NO, the variable k is initialized to “1”(step S27).

[0079] Next, it is determined whether or not to be ∇X(k)>0.9*DXmax (stepS28). If NO, the variable k is incremented by “1” (step S29), and theprocessing of step S28 is repeated. If YES, kth data is extracted as thecharacterizing point, and a flag is set to this data (step S30).

[0080] Next, it is determined to be k<K (step S31). If YES, the variablek is incremented by “1”, and the processing of step S28 is performed. IfNO, the processing for extracting the characterizing point is finished,and the processing of step S4 of FIG. 4 is performed.

[0081] Thus, in the flowchart of FIG. 10, the divergence ∇X(k) iscalculated for each data in the file. After the divergence maximum valueDXmax is calculated, all the data having the divergence equal to or morethan 90% of the divergence maximum DXmax is extracted as thecharacterizing points.

[0082] The characterizing points are necessarily not locations havinglarge divergence. The characterizing points may be extracted based onsimply data size. Or the characterizing points may be extracted based onthe other methods.

[0083] Thus, in the first embodiment, when the data is compressed, thedata except for the characterizing points is quantized, and when thesame quantized data is included at the same address location of thepreviously-compressed file, the quantized data is replaced with the filenumber of the previously-compressed file. Therefore, it is possible tocompress data at high efficiency.

[0084] (Second Embodiment)

[0085] A second embodiment retrieves data compressed by the methoddescribed in the first embodiment into the original data.

[0086]FIG. 12 is a block diagram showing schematic configuration of anembodiment of a data retrieving apparatus according to the presentinvention. The data retrieving apparatus of FIG. 12 has a quantized dataretrieving part 4 for converting the other file numbers in thecompression file into the quantized data, and a data retrieving partbefore quantization 5 which carries out simulation by settingnon-quantized data (data expressing characterizing points) in thecompression file as fixed values and setting quantized data (data exceptfor characterizing points) in the compression file as initial values,and retrieves data before quantization from quantized data in thecompression file.

[0087]FIG. 13 is a flowchart showing processing procedure of the dataretrieving apparatus described in FIG. 12. First of all, user'sretrieving request of nth compression file from the compressed filegroup is accepted (step S41), the file is loaded (step S42).

[0088] Next, it is determined whether or not the total numbers N offiles is larger than “1” (step S43). If YES, the file number included inthe loaded file is retrieved into the original quantized data (stepS44).

[0089] When determined NO in step S43, because the file number is neverincluded in the file, the processing of step S44 is omitted. Ifdetermined NO in step S43, or the processing of step S44 is finished,the retrieving calculation of the file is performed based on thecharacterizing points (step S45). A detail of the retrieving calculationwill be described later. Next, the flag for designating the characteringpoints is removed from the retrieved file (step S46), and then theretrieving data is outputted (step S47).

[0090]FIG. 14 is a diagram of modifying processing procedure ofretrieving data. Non-quantized data expressing the characterizingpoints, quantized data except for the characterizing points, and theother file numbers except for the characterizing points are mixed in thecompression file before retrieving data (state 3).

[0091] First of all, the other file numbers are converted into thecorresponding quantized data (state 2). Next, the characterizing pointsare set as fix values, and the quantized data is converted into realvalues as initial values. The simulation is carried out based ontogether preserved simulation information. Therefore, the quantized datais retrieved into the original data, and the original smoothdistribution as shown in FIG. 6 is retrieved based on the roughdistribution as shown in FIG. 7 (state 1).

[0092] Next, the flags designating the characterizing points are removedfrom the retrieved file to output the retrieving data (state 0).

[0093] As shown in the present embodiment, by setting the characteringpoints as the fixed value and the quantized data as the initial value,it is possible to begin the calculation from the state near a realvalue, and to obtain data distribution at 10 times speed than that ofthe ordinary simulation.

[0094] Furthermore, because only the system in which applications suchas the simulator are installed can retrieve data until level one, it ispossible to prevent data steal, thereby improving security performance.

[0095] A method of retrieving data from state 2 to state 1 of FIG. 14will be hereinafter described in detail. In the simulation, the equationto be solved is often converted into an algebraic equation by performingdiscrete processing, and answers are obtained by matrix solution. Thecalculation procedure is described as AX=B by matrix form, as shown inFIG. 15. A is a matrix of K*K, X and B are a column vector having Kpieces of elements, and X is an unknown letter.

[0096] It is assumed that the element X4 of the column vector X of k=4is the characterizing point. In this case, if 4 lines 4 columns of thematrix A are “1” and all the columns of the same line are “0”, the 4thelement of the column vector B becomes fixed value.

[0097] In the present embodiment, data which is the elements except forX4 in the column vector X and except for the characterizing points isset to be the initial value converted from the quantized data into areal number.

[0098] For example, in analysis of a semiconductor device as shown inFIG. 16, it is assumed that lattice points included in the illustratedregions are the characterizing points with regard to the physicalquantity X. Data compression by the quantization or the replacement ofthe file number is not performed with regard to the physical quantity Xon these lattice points. The physical quantity of one characterizingpoint in the region of FIG. 16 is set to be X4.

[0099] In the case of analyzing two dimension structure, as generallyshown in FIG. 17, an algebraic equation as shown in equation (4) isderived on the characterizing points by using the physical quantitiesXN, XS, X3 and X5 on the lattice points from right to left or up anddown of the physical points having the physical quantity X4.

AN·XN+A3·X3+A4·X4+A5·X5+AS·XS=B4  (4)

[0100] The equation (4) is the equation in the case that a value of X4is not decided and the case of performing the calculation by taking intoconsideration interactions between the surrounding lattice points. Whenthe lattice point having the physical quantity X4 is the characterizingpoint, and it is unnecessary to update the value X4, that is, X4 isdealt as a fixed value, X4 becomes the fixed value by setting to beA4=1, A5=0, AS=0 and B4=fixed value.

[0101] When the values of the lattice points except for X4, for example,XN or X5 are not the characterizing point, these values are thequantized value, and deteriorate compared with the original real value.However, because XN and X5 are values near the original values, thesevalues are substituted for the corresponding element of the columnvector of X of FIG. 15 as the initial value. In this stage, because leftside and right side of a determinant of FIG. 15 are not equal to eachother, by using the ordinary matrix solution, the elements of X columnvector are approximated the real value by repeated calculation so thatleft side becomes equal to right side.

[0102] At this time, the values of the characterizing points are not atall updated between the repeated calculation. Generally, there is acharacteristics in which periphery of points which are not updated getsclose to the real value by a few repeated calculation. Because of this,it is expected that as the characterizing points are abound, therepeated number of times decreases.

[0103] Furthermore, with regard to the physical quantity on the latticepoints except for the characterizing points, although the physicalquantity may not be a real value, a value near the real value is givenas the initial value. Because of this, it is expected that the realvalue is obtained by a few repeated calculation in totality.

[0104] For example, a method of mathematically solving Poisson equationof the following equation (5) by matrix solution will be describedhereinafter.

∇.å∇ø=−q(p−n+Nd−Na)  (5)

[0105] Here, å is permittivity, ø is potential, q is unit elementarycharge, p is hole density, n is electron density, Nd is donor density,and Na is accepter density.

[0106] When equation (5) is numerically solved by matrix solution,discrete processing of equation (5) is performed. For example, as shownin FIG. 18, when four lattice points of from right to left or up anddown of the characterizing points with the physical quantity ø4 have thephysical quantities øN, øS, ø3 and ø5, respectively, equation (6) isobtained by the discrete processing of equation (5).

ANøN+A3ø3+A4ø4+A5ø5+ASøS=B4  (6)

[0107] Here, each parameter of equation (4) is expressed by equations(7)-(14).

AN=ånä/Ärn  (7)

AS=åsä/Ärs  (8)

A3=åeä/Äre  (9)

AS=åsä/Ärw  (10)

A4=−AN−AS−A3−A5  (11)

B4=−äxäy(p4−n4+Nd4−Na4)  (12)

äx=(Äre+Ärw)/2  (13)

äy=(Ärn+Ärs)/2  (14)

[0108] In the present embodiment, if X4 is a fixed point, X4=fixed valueis established by setting to be AN=0, A3=0, A4=1, A5=0, AS=0 andB4=fixed value.

[0109] Thus, in the second embodiment, data of the characterizing pointis set to be the fixed value, the initial value which converts dataexcept for the characterizing points from the quantized data into realnumber is set, and then the repeated calculation by the simulation isperformed to retrieve the original data. Because of this, it is possibleto shorten the processing time necessary for retrieving data.

[0110] In principle, it is possible to retrieve the original data ifthere is only data of the characterizing points. Because of this,without setting the above-mentioned initial value, the simulation may beperformed by setting data of the characterizing points as the fixedvalue. In this case, compared with the case of setting the initialvalue, it takes too much time until the solution converges. Accordingly,if data retrieving at high speed is required, as described above, dataof the characterizing points is set to be the fixed value, the initialvalue which converts data except for the characterizing points from thequantized data into real number is set, and then the repeatedcalculation by the simulation may be performed to retrieve the originaldata.

[0111] (Third Embodiment)

[0112] A third embodiment does not preserve the physical quantitycapable of retrieving data based on a prescribed retrieving rule,thereby reducing the amount of data to be preserved.

[0113]FIG. 19 is a flowchart showing data compression processingprocedure in the third embodiment according to the present invention.The flowchart of FIG. 19 performs the processing of step S10 after theprocessing of step S2, and then performs step S3 a instead of step S3,compared with the flowchart of FIG. 4.

[0114] In step S10, the physical quantity is deleted in accordance withthe designated compression level from the loaded file. For example,there are seven types of levels 1-7, and compression ratio is differentfor each level. As the compression ratio is high, the deleted physicalquantity increases. in step S3 a, data of the characterizing points isextracted from the physical quantity not deleted in the file. When theprocessing of step S3 a is finished, the same processings as those ofstep S4-S9 of FIG. 4 are performed.

[0115]FIG. 20 is a conceptual diagram of data compression processingprocedure described in FIG. 19. It is assumed that the physicalquantities 1-4 exist in nth file. For example, the physical quantity 4is deleted in accordance with the designated compression level, andextraction of the characterizing points, quantization and replacement tofile number are carried out with regard to the remaining physicalquantities 1-3.

[0116]FIG. 21 is a flowchart showing data retrieving processingprocedure in the third embodiment according to the present invention.The flowchart of FIG. 21 performs the processing of step S48 after theprocessing of step S46, and performs the processing of step S47 afterthe processing of step S48, compared with the flowchart of FIG. 13.

[0117] In step S48, the deleted physical quantity is retrieved based ona prescribed retrieving rule. Here, the retrieving rule is a rule forretrieving the physical quantity not preserved, and is derived from thephysical model.

[0118]FIG. 22 is a conceptual diagram of data retrieving processingprocedure described in FIG. 21. First of all, the other file number isconverted into the quantized data, and then data before quantization isretrieved based on the characterizing points and the quantized data.Next, the deleted physical quantity 4 is retrieved based on the physicalquantities 1-3 not deleted.

[0119] Thus, in the third embodiment, the physical quantity easilyobtained by the simulation is not preserved. Because of this, it ispossible to reduce the amount of data preservation and to save storagearea of a recording medium.

[0120] The above-mentioned data compression apparatus and dataretrieving apparatus may be composed of hardware or software. In thecase of being composed of software, the program for realizing thefunction of the data compression apparatus and data retrieving apparatusmay be contained in recording mediums such as a floppy disk or a CD-ROM,in order to be read out and execute by a computer. The recording mediumis not limited to portable type of mediums such as magnetic disks oroptical disks. The fixed type of mediums such as a hard disk drive or asemiconductor memory may be used.

[0121] The program for realizing the function of the above-mentioneddata compression apparatus and data retrieving apparatus may bedelivered via communication lines including radio communication such asan internet. Furthermore, the program may be delivered at a state ofencoding, modulating or compressing the program, via a fixed-line orradio-line such as the Internet, or while containing the program in therecording medium.

What is claimed is:
 1. A data retrieving method of retrievingcompression data including non-quantized data expressing characterizingpoints and quantized data except for said characterizing points,comprising: carrying out simulation by setting said non-quantized dataas fixed values, if necessary based on said quantized data; andretrieving data before quantization from said quantized data based on aresult of carrying out said simulation.
 2. The data retrieving methodaccording to claim 1, wherein data relating to the physical quantity notpreserved is retrieved by using said retrieved data before quantizationand a prescribed retrieving rule.
 3. A data retrieving method ofretrieving compression data including non-quantized data expressingcharacterizing points, quantized data except for said characterizingpoints, and pointer data related to certain quantized data comprising:converting said pointer data into the corresponding quantized data;carrying out simulation by setting said non-quantized data as fixedvalues and an initial value based on said quantized data; and retrievingdata before quantization from said quantized data based on a result ofcarrying out said simulation.
 4. The data retrieving method according toclaim 3, wherein data relating to the physical quantity not preserved isretrieved by using said retrieved data before quantization and aprescribed retrieving rule.
 5. The data retrieving method according toclaim 3, wherein the number of bits of said pointer data is fewer thanthe number of bits of said certain quantized data.
 6. The dataretrieving method according to claim 3, wherein each of said quantizeddata is managed by file number, and said pointer data is file number ofsaid quantized data except for the corresponding quantized data.
 7. Thedata retrieving method according to claim 3, wherein said pointer dataexpresses each simulation location in the case of carrying outsimulation by dividing simulation objects into mesh shape.
 8. A datacompression method, comprising: extracting data expressingcharacterizing points from a plurality of data as objection ofcompression; generating quantized data to quantize data except for dataexpressing said characterizing points among said plurality of data asobjection of compression; converting the same types of quantized dataincluded in said quantized data into pointer data having the number ofbits fewer than that of said quantized data, said pointer data beingrelated to the corresponding quantized data.
 9. The data compressionmethod according to claim 8, wherein data according to the designatedcompression level is deleted from said plurality of data as objection ofcompression; and data expressing said characterizing points is extractedfrom data except for said deleted data, among said plurality of data asobjection of compression.
 10. The data compression method according toclaim 8, wherein said plurality of data as objection of compression aredata showing a result of simulation.
 11. The data compression methodaccording to claim 8, wherein data expressing said characterizing pointsis extracted by setting a maximum value of variation ratio for a maximumvalue of data or the adjacent relating data as a reference.
 12. The datacompression method according to claim 10, wherein a maximum value ofdivergence showing a location where space variation of spacedistribution is sharpest is detected among said plurality of data asobjection of compression; and data with the divergence value in whichratio for the maximum value of divergence is equal to or more than aprescribed value is extracted as said characterizing points.
 13. Thedata compression method according to claim 8, wherein each of saidquantized data is managed by file number; and said pointer data is filenumber of the quantized data except for the corresponding quantizeddata.
 14. The data compression method according to claim 13, whereinsaid pointer data expresses each simulation location in the case ofcarrying out simulation by dividing a simulation object in mesh shape.15. A data retrieving apparatus which retrieves compression dataincluding non-quantized data expressing characterizing points andquantized data except for said characterizing points, comprising: asimulation part for carrying out simulation by setting saidnon-quantized data as fixed values and if necessary setting initialvalues based on said quantized data; and a first data retrieving partfor retrieving data before quantization from said quantized data, basedon a result of said simulation.
 16. The data retrieving apparatusaccording to claim 15, further comprising a second data retrieving partfor retrieving data relating to physical quantity not preserved, byusing said retrieved data before the retrieved quantization and aprescribed retrieving rule.
 17. A data retrieving apparatus whichretrieves compressing data including non-quantized data expressingcharacterizing points, quantized data except for said characterizingpoints, and pointer data related to certain quantized data, comprising:a quantized data converting part which converts said pointer data intothe corresponding quantized data; a simulation part for carrying outsimulation by setting said non-quantized data to be fixed values andinitial values based on said quantized data; and a first data retrievingpart for retrieving data before quantization from said quantized databased on the result of the simulation.
 18. The data retrieving apparatusaccording to claim 17, further comprising a second data retrieving partfor retrieving data relating to physical quantity not preserved by usingsaid retrieved data before quantization and a prescribed retrievingrule.
 19. A data compression apparatus, comprising: a data extractionpart for extracting data expressing characterizing points from aplurality of data as objection of compression; a quantized datagenerating part which generates quantized data obtained by quantizingdata except for data expressing said characterizing points among saidplurality of data as objection of compression; and a pointer convertingpart for converting the same types of quantized data included in saidquantized data into pointer data having the number of bits fewer thanthat of the quantized data, said pointer data being related to thequantized data.
 20. The data compression apparatus according to claim19, further comprising data deleting part for deleting data according tothe designated compression level; wherein said data extracting partextracts data expressing said characterizing points included in dataexcept for said deleted data among said plurality of data as objectionof compression.